Note 20 - Assets and Liabilities Measured and Reported at Fair Value - Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Securities available-for-sale	$ 470,738	$ 436,995
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	470,738	436,995
US Government-sponsored Enterprises Debt Securities [Member]
Securities available-for-sale	209,944	261,039
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	209,944	261,039
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities available-for-sale	193,861	146,277
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	193,861	146,277
US States and Political Subdivisions Debt Securities [Member]
Securities available-for-sale	17,036	29,679
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	17,036	29,679
Fair Value, Recurring [Member]
Securities available-for-sale	470,738	436,995
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	470,738	436,995
Interest rate swaps	2,696	1,035
Total assets	473,434	438,030
Interest rate swaps	2,767	543
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	49,897	0
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	49,897	0
Interest rate swaps	0	0
Total assets	49,897	0
Interest rate swaps	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	420,841	436,995
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	420,841	436,995
Interest rate swaps	2,696	1,035
Total assets	423,537	438,030
Interest rate swaps	2,767	543
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale	0	0
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	0	0
Interest rate swaps	0	0
Total assets	0	0
Interest rate swaps	0	0
Fair Value, Recurring [Member] | US Treasury and Government [Member]
Securities available-for-sale	49,897
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	49,897
Fair Value, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	49,897
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	49,897
Fair Value, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	0
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	0
Fair Value, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale	0
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	0
Fair Value, Recurring [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Securities available-for-sale	209,944	261,039
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	209,944	261,039
Fair Value, Recurring [Member] | US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	0	0
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	0	0
Fair Value, Recurring [Member] | US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	209,944	261,039
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	209,944	261,039
Fair Value, Recurring [Member] | US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale	0	0
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	0	0
Fair Value, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities available-for-sale	193,861	146,277
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	193,861	146,277
Fair Value, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	0	0
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	0	0
Fair Value, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	193,861	146,277
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	193,861	146,277
Fair Value, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale	0	0
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	0	0
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]
Securities available-for-sale	17,036	29,679
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	17,036	29,679
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	0	0
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	0	0
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	17,036	29,679
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	17,036	29,679
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale	0	0
Securities available for sale (amortized cost of $469,313 in 2019 and $443,742 in 2018)	$ 0	$ 0